Maestro FZ1-B 4 trans restoration, factory schem and pcb photos inside

[PRR]

...If you go to FSB, then find the section "Davidoff Library", you will find a thread called "Complete Maestro Service Manual, indexed PDF".  The PDF contains schematics for all the versions of Fuzz-Tones (perhaps not all correct despite the fact it's Maestro's documents).

The ban on linking to "FSB" has been lifted.
Thread: https://www.freestompboxes.org/viewtopic.php?t=31096

...That's a "known" version.  Maestro call it the FZ-1B version 1 but some people refer to it as the two transistor FZ-1B.  It's actually quite different to the FZ-1B version 2 in this thread.

Not remotely like the 4 transistor version.

[Rob Strand]

FYI, jimi posted some voltage measurements in this post

maestro fz1-b info
https://www.diystompboxes.com/smfforum/index.php?topic=98520.0

His Q3 is actually Q4 on the schematic.  Unfortunately he didn't post a voltage for the actual Q3 on the schematic.

From his voltages I could confirm the gain of the transistors aren't too far off the GE 2N3392 plot I posted earlier.  And there is some evidence of hFE drop at low currents.

Jimi mentions the transistors are marked 2298n.  I have seen transistors marked 2298R.
On the older schematics attached to the units the transistor are given
as Maestro part number 991-002298.   So the 2298 comes from that.
Not sure if they are really 2N3392s.  The 2N3392 appears on later schematics,
which has a different Maestro Part number 991-042017-001.

I simulated a collector voltage on Q3 of about 0.9V to 1.0V.  Where the actual voltage
is dependent on a number of factors including the diode.    The squelch circuit acts as a kind
of DC servo for the collector voltage.  Vc3 ~ VD + VBE4 + drop across 680k ~ 0.9V to 1.0V at low currents.

With such low current around Q3 and Q4 the meter loading may affect the voltages, especially a 1M input impedance DMM.

[zbt]

...If you go to FSB, then find the section "Davidoff Library", you will find a thread called "Complete Maestro Service Manual, indexed PDF".  The PDF contains schematics for all the versions of Fuzz-Tones (perhaps not all correct despite the fact it's Maestro's documents).

The ban on linking to "FSB" has been lifted.
Thread: https://www.freestompboxes.org/viewtopic.php?t=31096

...That's a "known" version.  Maestro call it the FZ-1B version 1 but some people refer to it as the two transistor FZ-1B.  It's actually quite different to the FZ-1B version 2 in this thread.

Not remotely like the 4 transistor version.

Its corrected here 
https://www.diystompboxes.com/smfforum/index.php?topic=119752.0
https://www.diystompboxes.com/smfforum/index.php?topic=61138.msg479711#msg479711

To complete FZ-1B v1

different from fuzz rite:
Fuzz Rite two common emitter, this Fuzz Tone would be common collector or buffer, and common emitter or boost
Not true bypass
Some mods
1. Make it true bypass
2. Diode mods, 1 on (1 diode), 2 off (no clip), 3 on (2 diode)
3. make R6 series with 1M pot as bias




66x52mm

[zbt]

5) A trace of the PCB in this thread agrees with the LucifersTrip's schematic:
  - the 3M3 going to gnd and the 680k between the Q4 base and the diode cathode.
  - the direction of the diode is as shown on the schematic(s):
    anode to Q3.c collector and diode cathode towards Q4.b.

also my mistake, here is the fix

[Rob Strand]

Looks good.  330k is correct.

I actually did this markup when I checked the 3M3 vs 680k to ground issue.  Had to look at some other on-line pics to confirm the cap values.  It also shows the transistor numbers (Q2 emitter = e2 etc) and the wire functions:

x-ray view:

[Rob Strand]

Something interesting about the Maestro Fuzz-Tone FZ-1B version 1 is the actual transistors on the PCB are marked 2N3860 but the later schematics in the Maestro service notes quote 2N3392 = Maestro p/n 991-042017-001.

For the Maestro Fuzz-Tone FZ-1B version 2 the schematics attached to the unit indicate Maestro p/n 991-002298 where as the Maestro service notes quote 2N3392 = Maestro p/n 991-042017-001.

Since the early Fuzz-Tone FZ-1B version 2 were made just after Fuzz-Tone FZ-1B version 1 we can
perhaps we can infer that Maestro p/n 991-002298 is actually 2N3860.  So the early Fuzz-Tone
FZ-1B version 1 actually use 2N3860.  It's a guess but it looks feasible.

If we look at the old GE datasheets for the 2N3860 and compare them to the 2N3392 we can see they
have some similarities as far as hFE and hFE dependency on the collector current goes.

Both have TO-98 packages

Nominal Data

    hFE @2mA    VCEO_max
2N3860    150 to 300    30V
2N3392    150 to 300    25V

GE data 2N3860 hFE vs collector current:

[zbt]

for this pcb





look just the green color of resistor, it confirm that LucifersTrip's schematic is the correct one

hFE @2mA    VCEO_max
2N3860    150 to 300    30V
2N3392    150 to 300    25V

except for FZ-1, FZ-1A
looks like it can be done using current transistors like 2N2222 and 2N3904 
Bass Brass Master, FZ-1Bv1, FZ-1Bv2, FZ-1S, and FZ-1M

https://www.maestroelectronics.com/en-US/Pedal/Fuzz-Tone/MOCFTP

Long live Maestro

[Rob Strand]

looks like it can be done using current transistors like 2N2222 and 2N3904

Yes, probably the best choice from easy to get parts.  Perhaps pluck out a few low gain units.

If you want to make things bit closer to the original units, Q3 and Q4 might still need tweaking. A lot of 2N2222's (and other 2222's) and 2N3904's still have a high hFE at low currents.   Maybe reduce the 470k collector resistor and/or increasing the 330k base resistor.  Soon find out when you play through the unit if it makes a noticeable difference.  Too long ago since I played with this one.